The red pepper on Rate My Professors indicates how physically attractive, or hot, the professor is. If the pepper is red, it generally means that the students find the professor to be above average in physical attractiveness.
Students, when rating a professor on Rate My Professors, can choose to rate a professor as "hot" or "not hot." If the professor in question has more "hot" ratings than "not hot," a red chili pepper is displayed in the profile. If he or she has more "not hot" ratings than "hot" ratings, the pepper is grayed out. As of November 2015, there is no way of seeing which "hotness" option students have selected, nor is there a way of seeing how many "hotness" votes a teacher has received.